Changes in the transfer RNA population of lens cells occur when a bovine lens epithelial cell differentiates into a lens cortex cell. One of these changes is the synthesis of a new phenylalanine transfer RNA species. We intend to compare this cortex-specific phe-tRNA with the epithelial cell phe-tRNA and the liver phe-tRNA by two dimensional electrophoresis of both T1 and pancreatic ribonuclease digests of these tRNAs. The ability of these tRNAs to transfer phenylalanine into alpha crystallin will also be compared using an in vitro, protein-synthesizing system which is programmed for the synthesis of alpha crystallin by exogenously supplied messenger RNA. Other tRNA differences will be tested in a similar manner. BIBLIOGRAPHIC REFERENCES: Ortwerth, B.J., G.R. Yonuschot, J.F. Heidlege, O.M.Y. Chu-Der, D. Juarez and C. Hedgcoth, Induction of a New Species of Phenylalanine Transfer RNA During Lens Cell Differentiation. Exp. Eye Res. (1975) 20,417-426. Juarez, H.D. Juarez, C. Hedgcoth and B.J. Ortwerth, Amounts of Isoaccepting Lysine tRNAs Change with the Proliferative State of Cells. Nature (1975) 254, 359-360.